"It is a really meaningful family relationship," said Ron Klain, who served as Biden's chief of staff during the first term and, in the second term, as the Obama’s coordinator for the Ebola epidemic.

The partnership has had its rough patches, but the contrast between Obama, “the disciplined, methodical thinker,” and Biden, “the back-slapping, emotional Irish American pol” has become a source of amicable teasing.

Said White House senior adviser Valerie Jarrett: "They trust one another and can be very honest with each other. They love each other."

Julie Smith, who served as the vice-president’s deputy national security adviser between 2012 and 2013, said that Biden “has learned to adapt to the president’s style,” while Obama has come to accept his second-in-command’s different approach.

“They’ve found a way to manage their differences,” said Smith, who directs the strategy and statecraft program at the Center for a New American Security. “They don’t have to lose sleep over this relationship, because they’re going to make it work.”

David Axelrod, the president’s former senior advisor, said the massive financial challenges the administration faced in its early years helped cement the bond between Obama and Biden.

“We came to office at such a miserably difficult time and had to face some very difficult challenges, and I think that’s part of what forged that relationship,” said Axelrod. “It was in this crucible of crisis where they really had to rely on each other.”

Speaking from the pulpit at the funeral Mass on Saturday, Obama told Beau Biden’s widow Hallie, his two children, and the rest of his family, along with more than a thousand mourners: “We are here to grieve with you, but more importantly, we are here because we love you.”

“To Natalie and Hunter – there aren’t words big enough to describe how much your dad loved you, how much he loved your mom. But I will tell you what, Michelle and I and Sasha and Malia, we’ve become part of the Biden clan,” he said.

“We’re honorary members now. And the Biden family rule applies. We’re always here for you, we always will be – my word as a Biden.”

Out of touch US President Barack Obama needs to forget golf and refocus.Getty